Localized spot lapping on a larger work surface area

ABSTRACT

An apparatus for lapping a portion of an exterior surface of a housing is described. The apparatus includes at least a lapping tool arranged to execute a lapping operation. The lapping tool takes the form of a lapping pad which includes a conduit through which slurry can be transported for local deposition on the housing during a lapping operation. The apparatus also includes a stage on which a workpiece in the form of a housing is mounted. During the lapping operation, slurry is passed through the slurry conduit in the lapping tool, the lapping tool and the housing are moved in various motions. In this way, a gradual transition region is created between an accessory region and the remainder of the housing.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and benefit under 35 U.S.C. 119(e)of U.S. Provisional Patent Application Ser. No. 61/603,177, filed Feb.24, 2012, entitled LOCALIZED SPOT LAPPING ON A LARGER WORK SURFACE AREA,the entire disclosure of which is hereby incorporated by reference inits entirety and for all purposes.

BACKGROUND

1. Technical Field

The present invention relates generally to the polishing of a threedimensional metal alloy object. More particularly, a method and anapparatus are described for polishing a portion of an exterior surfaceof a housing of a portable electronic device to form a visuallycontinuous flat top edge surface.

2. Related Art

The proliferation of high volume manufactured, portable electronicdevices has encouraged innovation in both functional and aestheticdesign practices for enclosures that encase such devices. Manufactureddevices can include a housing that provides an ergonomic shape andaesthetically pleasing visual appearance desirable to the user of thedevice. Exterior surfaces of housings of portable electronic devices canbe shaped by computer numerically controlled machinery and can includecombinations of flat regions and curved regions as well as accessoryregions such as logos and the like. Irregularities in the surface of thesurface between the accessory region and the remainder of the housingcan result in an unacceptable appearance due to visual artifacts causedby physical transitions between the two regions. For example, if theaccessory region and the remainder portion of the housing are separatedby an abrupt change in surface finish, then this change can be visiblerendering an unappealing transition between the accessory region and therest of the housing.

Thus there exists a need for a method and an apparatus for polishing asurface of a housing resulting in a surface with a consistent surfacevariation within a tolerance required to achieve a desired surfaceappearance upon finishing.

SUMMARY

The embodiments relate to a system, method and apparatus for creating agradual transition region between a polished accessory region and theremainder of a surface portion of a metal housing.

In one embodiment, an apparatus for creating a gradual transition regionbetween an accessory region and a surrounding exterior surface region ofa housing is disclosed. The apparatus includes a lapping tool. Thelapping tool includes a lapping pad. The lapping pad includes at leastthe following: (1) a centerpoint surrounded by a central portion, and(2) a peripheral portion. During a lapping operation the centerpoint ofthe lapping pad is compelled to follow a lapping path, the lapping pathincludes a number of lapping segments. Each lapping segmentsubstantially crosses the accessory region at an angle different than apreceding lapping segment and each lapping segment puts a peripheralportion of the lapping pad in tangential contact with a central area ofthe accessory region, thereby creating the gradual transition region.

In another embodiment a manufacturing method is disclosed. Themanufacturing method includes at least the following steps: (1) mountinga housing to a stage, where the housing includes at least a firstregion, a second region surrounded and defined by the first region, anda transition region disposed between the first region and the secondregion; (2) positioning a lapping tool in physical contact with aportion of the second region during a lapping operation, the lappingtool including a lapping pad having a central portion and a peripheralportion; and (3) finishing the transition region by causing the lappingpad to follow a lapping path, the lapping path comprising a number oflapping segments, each lapping segment substantially crossing the secondregion at an angle different than a preceding lapping segment and eachlapping segment putting the peripheral portion of the lapping pad intangential contact with a central area of the second region.

In yet another embodiment a lapping assembly is disclosed. The lappingassembly includes at least the following: (1) a lapping tool comprisinga rotating lapping plate coupled to a lapping pad; (2) a force sensorcoupled to the lapping tool for regulating pressure exerted by thelapping tool; and (3) a stage configured to maneuver a housing in aplane substantially parallel with the lapping pad during a lappingoperation, the housing having an exterior surface with an accessoryregion and a surrounding surface region. During a lapping operation thelapping pad is compelled to follow a lapping path, the lapping pathincludes a number of lapping segments, each lapping segmentsubstantially crossing the accessory region at an angle different than apreceding lapping segment and each lapping segment putting a peripheralportion of the lapping pad in tangential contact with a central area ofthe accessory region, thereby creating a gradual transition regionbetween the accessory region and the surrounding surface region.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments will be readily understood by the following detaileddescription in conjunction with the accompanying drawings, wherein likereference numerals designate like structural elements, and in which:

FIG. 1A-1B illustrate a housing with an accessory region;

FIGS. 1C-1E illustrate cross-sectional view of accessory regions;

FIG. 2 illustrates one embodiment of a lapping machine assembly;

FIG. 3 illustrates a perspective view of one embodiment of a lappingtool;

FIG. 4A illustrates a cross-sectional view of a lapping tool;

FIG. 4B illustrates a lapping tool configured to deliver slurry to anumber of slurry conduit branches distributed across the surface of alapping plate;

FIG. 4C illustrates a lapping tool configured with a variableflexibility lapping plate;

FIG. 4D illustrates a lapping tool with an externally arranged slurrydelivery conduit;

FIG. 5 illustrates a top view of one possible center weighted patternthat can be employed during a lapping operation;

FIG. 6 illustrates alternative center weighted paths that can be usedwith previously described embodiments; and

FIG. 7 illustrates a flow chart detailing a representative lappingprocess in accordance with the other previously described embodiments.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

The present invention relates generally to the polishing of a threedimensional metal alloy object. More particularly, a method and anapparatus are described for polishing an exterior surface of a metalalloy housing of a portable electronic device to form a combination of aflat top edge surface, a curved edge surface and a flat bottom surface.

In the following description, numerous specific details are set forth toprovide a thorough understanding of the present invention. It will beapparent, however, to one skilled in the art that the present inventionmay be practiced without some or all of these specific details. In otherinstances, well known process steps have not been described in detail inorder to avoid unnecessarily obscuring the present invention.

High volume manufactured portable electronics devices can includecomputer numerically controlled (CNC) machined metal alloy parts withvarious geometrically shaped surfaces. Representative portableelectronic devices can include portable media players, portablecommunication devices, and portable computing devices, such as an iPod®,iPhone° and iPad® manufactured by Apple, Inc. of Cupertino, Calif. Boththe tactile and visual appearance of a portable electronics device canenhance the desirability of the portable electronic device to theconsumer. Housings can be used that include metal alloys which canprovide a lightweight material that exhibits desirable properties, suchas strength and heat conduction well suited for housings of portableelectronic devices. A representative metal alloy can include an aluminumalloy. Both the tactile and visual appearance of a portable electronicsdevice can enhance the desirability of the device to the consumer. Acosmetic outer layer machined from a metal alloy can be cut to a desiredshape and polished to a desired reflective and/or matte appearance. Insome embodiments, a continuously smooth shape having a uniformlyvisually smooth appearance is desired.

High volume manufacturing can benefit greatly from minimized processingtime. Machining an aluminum billet to form the exterior surface of ahousing of a portable electronic device using a single cutting tool canreduce the processing time required. Machining with a single continuousoptimized path can result in a “rough” cut surface that can requireminimal sanding and polishing to produce a visually smooth finish withno visually discernible breaks between regions having different crosssections. Curved regions can transition smoothly into flat regionsincluding along corner areas without any visual change in surfaceappearance. In some cases specific regions along an exterior surface ofthe housing require additional polishing operations to achieve a desiredpolishing effect across that surface. Since polishing operationsgenerally result in material removal, polishing operations targeting adiscrete area for a smoother or shinier finish can cause a surfacevariation in the previously continuous surface of the housing.Unfortunately, in some cases the variation can cause an abrupt changebetween surface areas that can mar the overall look and feel of thehousing.

In one embodiment a lapping process can be utilized to create a gradualtransition region between the aforementioned accessory region and theless thoroughly polished remainder of the housing. The process can bereferred to as spot lapping as the lapping operation is focused on aparticular portion of the housing. A lapping tool associated with thelapping process is aligned parallel with the surface of the housing andmaneuvered with respect to the surface of the housing during the lappingoperation by a stage. The stage permits maneuvering of the housing in anumber of degrees of freedom allowing movement in at least an X-Y plane.The lapping tool can be a rotary polishing tool configured to spin anabrasive pad across the surface of the housing. By maneuvering thelapping tool along a lapping path with respect to the housing such thatefficient material removal portions of the lapping tool spends more timeover a central portion of the depression than over peripheral portionsof the depression a gradual transition region can be established,thereby smoothing an abrupt visual or tactile change between theaccessory region and the remainder of the surface of the housing.

Various embodiments of lapping methods suitable for establishing asmooth transition region across a portion of a surface of a metalsubstrate are discussed below with reference to FIGS. 1A-7. However,those skilled in the art will readily appreciate that the detaileddescription given herein with respect to these figures is forexplanatory purposes as the full extent of the embodiments goes beyondthese limited descriptions.

FIG. 1A illustrates a housing with an accessory region. For exemplarypurposes the housing will be referred to as an aluminum housing, but itshould be noted that the embodiments described within this applicationcan be applied to any substrate well suited to lapping operations.Aluminum housing 100 includes accessory region 102. Accessory region 102in this embodiment is a finely polished or in some embodiments mirrorpolished region of aluminum housing 100. Consequently, aluminum housing100 includes abrupt transition region 104 between accessory region 102and surrounding surface region 106. Abrupt transition region 104 canarise from additional polishing operations targeted only at accessoryregion 102 of aluminum housing 100 for achieving the highly polishedsurface finish associated with accessory region 102. In one embodimentaccessory region 102 can have a mirror polished finish while surroundingsurface area 106 can have a matte, bead blasted, anodized consistency.Abrupt transition region 104 can mar the overall look and feel of thedevice. Depending on the size and abruptness of abrupt transition region104, this region can cause a significant tactile disruption across anotherwise smooth and continuous surface of aluminum housing 100. Insteadof experiencing a continuously smooth surface an abrupt change insurface consistency is encountered by anyone moving a finger betweenaccessory region 102 and the more coarsely textured surrounding surfaceregion 106. FIG. 1B illustrates a housing 100 after undergoing a lappingoperation. Abrupt transition region 104 is replaced by gradualtransition region 108, which expanding radially outward from accessoryregion 102. In this way a gentle tactile transition from a smooth to amore coarse texture can be established, thereby resulting in a moreappealing look and feel to aluminum housing 100.

FIG. 1C illustrates a cross sectional view of aluminum housing 100 asdefined in FIG. 1A along cross section A-A. In this depiction abrupttransition region 104 is embodied as a rapid change in texture betweenaccessory region 102 and surrounding surface region 106. Surface region106 includes multiple scalloped features associating a significantlyless polished surface finish with surrounding surface region 106 thanthe surface finish disposed across accessory region 102. In someembodiments accessory region 102 can be disposed slightly lower thansurrounding surface region 106 as a result of increased material removalresulting from additional polishing operations. FIG. 1D shows oneembodiment of gradual transition region 108 achieved after a lappingoperation. Gradual transition region 108 can be spread over a relativelyshort distance in this embodiment. As will be discussed below this canbe achieved by varying a lapping path of a lapping tool used to creategradual transition region 108. This embodiment can be desirable when ashorter lapping operation is desired, and/or when only a minimal amountof material removal is desired. In some embodiments a short gradualtransition region can result in a more noticeable transition than theone similar to gradual transition region 108 as depicted in FIG. 1E.FIG. 1E shows a relatively more gradual transition region 108. While alonger transition region results in additional material removal it canalso beneficially allow for a more seamless gradual transition region108. Such an effect can be desirable when such a surface should havelittle or no tactile cues to a holder of aluminum housing 100 of changesin surface finish.

FIG. 2 illustrates one embodiment of lapping machine assembly 200.Lapping machine assembly 200 includes lapping tool 202. In thisembodiment of lapping machine assembly 200 lapping tool 202 ismechanically coupled to tool holder 204. Tool holder 204 is configuredto maneuver lapping tool 202 in the Z-axis. By maneuvering lapping tool202 in the Z-axis lapping tool 202 can be put into direct contact withaluminum housing 100. Tool holder 204 can also be configured withsufficient power to exert force on aluminum housing 100 by lapping tool202. Exertion of force upon aluminum housing 100 can be regulated by aforce sensor. The force sensor is used to ensure a consistent amount ofpressure is exerted between lapping tool 202 and aluminum housing 100.The force sensor can be any force sensor capable of regulating pressurebetween lapping tool 202 and aluminum housing 100 such as for example aweight based, spring based or even pneumatically driven force sensor.Aluminum housing 100 can be mechanically coupled to stage 206. Stage 206can be configured to translate aluminum housing 100 in any directionwithin an X-Y plane during a lapping operation. The X-Y plane can bedefined as a plane parallel to the surface of housing 100. In someconfigurations in addition to translation of aluminum housing 100 withinthe X-Y plane stage 206 can be configured to rotate housing 100 duringthe lapping operation. This rotation motion can maintain a surfaceportion of aluminum housing 100 within the X-Y plane while the stagealso maneuvers aluminum housing 100 in an X-direction, a Y-direction ora combination of both directions during a lapping operation. Rotation ofaluminum housing 100 can be in an axis of rotation not in alignment withan axis of rotation associated with lapping tool 202. By establishing asmall mismatch between the rotational axes of aluminum housing 100 andlapping tool 202 while simultaneously maneuvering housing 100 along alapping path within the X-Y plane, the resulting path of lapping tool202 across the surface of aluminum housing 100 can be randomized. Forexample, moving aluminum housing 100 in a star shaped or spiral patternwhile aluminum housing 100 is being rotated can result in a randomized,lapping path.

FIG. 3 illustrates a perspective view of one embodiment of lapping tool202. Lapping tool 202 includes lapping pad 302. Lapping pad 302 is anabrasive pad suited to match desired surface characteristics of thesurface of the substrate to which it will be applied. In one set oftrials lapping pads having thicknesses of between about 1 and 5 mm anddiameters of between 35 and 50 mm were used. Dimensions of lapping pad302 ultimately depend upon the size of the area over which a polishingeffect is desired. Polishing pad 302 is mechanically coupled to lappingplate 304. Lapping plate 304 has a lower surface sized to match lappingpad 302. Lapping pad 304 can be configured to spin at rotational speedsof between 400 and 1200 rpm, while in some embodiments aluminum housing100 (not shown) spins relatively slowly at between about 10 and 30 rpm.Lapping plate 304 also includes slurry delivery channels which will bemore fully detailed in subsequent drawings. Lapping tool 202 alsoincludes slurry delivery fitting 306 which allows slurry to be deliveredto a lapping surface by the lapping tool.

FIG. 4A illustrates a cross-sectional side view of lapping tool 400.Lapping tool 400 includes lapping pad 402 and lapping plate 404 aspreviously discussed. Lapping tool 400 also includes slurry conduit 406with an accompanying slurry delivery inlet 408. Slurry conduit 406routes slurry from slurry inlet 408 to lapping pad 402. This routingsystem can keep lapping pad 402 and a surface of aluminum housing 100well covered in slurry during a lapping operation. However, throughtrials it was determined that a gravity feed alone is generally notenough to induce continuous flow of slurry to a lapping surface. Whenslurry conduit 406 is configured to run straight down the center oflapping tool 400 centrifugal force can cause the slurry to becometrapped in slurry conduit 406. Consequently, slurry conduit branches 410can be built into lapping tool 400. Slurry conduit branches arranged ina manner so that the branches are not perpendicular to rotation oflapping plate 404 can use the centrifugal force incidental to thespinning motion of lapping plate 404 to actually increase flow of slurryto a surface undergoing a lapping operation. In one embodiment a rate ofbetween 50 and 100 mL/min of slurry was found to be sufficient for alapping operation. It should be noted that in addition to gravity fedslurry delivery that pressurized slurry delivery can also be used toovercome problems with centrifugal force and through tool slurrydelivery.

FIG. 4B illustrates lapping tool 450 configured to deliver slurry to anincreased number of locations across a surface of lapping pad 402 byhaving a number of slurry conduit branches 410 distributed across thesurface of lapping plate 404. In this way slurry delivery to lapping pad402 can be accomplished in a more even manner. It should be noted thatlapping pad 402 includes chamfered edges 412 as depicted. In a normallapping operation lapping pad will be held substantially parallel to thesurface upon which it is lapping. In the event of a small misalignmentchamfered edges 412 can reduce the likelihood of an edge of lapping pad402 putting a mark or blemish in a surface portion of aluminum housing100. In some embodiments lapping plate 404 can have rounded corners 414to further reduce the likelihood of scraping of aluminum housing 100 bylapping plate 404.

FIG. 4C illustrates a lapping tool 460 configured with a variableflexibility lapping plate 462. In one embodiment lapping plate 462 canbe configured to have a rigid central portion 464 coupled to a flexibleperipheral portion 466. In this way peripheral portions of lapping pad402 can experience a reduced amount of force, thereby resulting in asmaller amount of material removal towards an edge portion of thecutting tool, thereby achieving a more gradual feathering effect thanmight otherwise be possible with a solid and rigid lapping plate 462. Inanother embodiment lapping plate 462 can be a composite plate havinggradually decreasing rigidity moving from a central portion of lappingplate 462 to an outer edge portion of lapping plate 462, therebyachieving a similar increase in feathering performance. Furthermore,lapping pad 402 can assume a dome shape as illustrated, thereby reducingforce applied by peripheral portions of lapping pad 402, thereby furtherincreasing feathering performance of lapping tool 460.

FIG. 4D illustrates an embodiment in which lapping plate 482 is onesolid metal material. For example, lapping pad 482 can be a single piecestainless steel lapping plate. Furthermore, slurry delivery conduits 408can be arranged laterally outside the lapping tool. Slurry conduits 408can deliver slurry around a peripheral portion of lapping tool 480,thereby covering the lapping path of the lapping tool with slurry priorto a lapping operation. While two slurry conduits are shown in thisillustration it should be noted that any number of slurry conduits 408can surround lapping tool 480 thereby evenly spreading slurry in anydirection lapping tool 480 is traversing. Lapping pad 484 can beconfigured to have a broader diameter than lapping plate 482. Since thisresults in lapping pad 484 extending past an edge portion of lapping pad482 a smaller amount of pressure can be asserted on an underlyingportion of aluminum housing 100, thereby increasing a feathering effectof lapping tool 480.

FIG. 5 illustrates a top view of one possible center weighted path 502that can be employed during a lapping operation. A stage can beconfigured to translate aluminum housing 100 in a manner matchinglapping path 502 with respect to lapping tool 504. Lapping tool 504makes a swath 506 as it translates across aluminum housing 100. Lappingpath 502 works particularly well because it aligns an edge portion oflapping tool 504 with a central portion of accessory region 102. Sincetrials have shown that peripheral portions of lapping tool 504 removematerial more quickly than central portions of lapping tool 504 thisconfiguration results in hitting a central portion of accessory region102 more heavily than outlying portions of accessory region 102.Furthermore, since lapping path 502 minimizes time spent by lapping tool504 at various peripheral portions of aluminum housing 100 a smoothfeathered pattern can be achieved across abrupt transition region 104,thereby creating a gradual transition region creating an illusion of acompletely smooth surface for aluminum housing 100. Furthermore, in somecases even a complex shape like the one depicted may result in minorlinear track marks being scribed into a surface portion of aluminumhousing 100. By rotating aluminum housing 100 in direction 508 whilepath 502 is being traced lapping path 502 can be further randomizedessentially creating curved lapping segments instead of straight linespaths into aluminum housing 100, thereby making lapping paths much moredifficult to discern.

It should be noted that in some embodiments multiple accessory regions102 can be present on one surface of aluminum housing 100. Given such aconfiguration a single lapping operation can be designed to covermultiple accessory regions 102 when they are in close proximity to oneanother. For example, in one embodiment an aluminum housing 100 with ashiny corporate logo proximate to a shiny line of text can be desired.When the text is in proximity to the logo abrupt transition regions 104of both the logo and the text can be removed in a single lappingoperation. It should also be noted that in a more complex configurationan extra degree of freedom can be added to a lapping machine assemblyallowing a lapping operation to be applied across a three dimensionalsurface. For example, a spline or curve shaped surface can also includeaccessory regions. As with a flat surface, abrupt changes between asurface finish of an accessory region and the remaining portions of ahousing can result in visual and tactile distractions. The extra degreeof freedom in the stage can allow blending across an abrupt transitionregion, thereby allowing aforementioned techniques such as the lappingpath to be applied to a three dimensional surface.

FIG. 6 illustrates alternative lapping paths that can be used withpreviously described embodiments. As depicted orbital, spiral, racetrack and figure eight patterns can all be used to apply more polishingeffect on an inner portion of an accessory region while more lightlypolishing peripheral portions of an accessory region, thereby creating agradual transition region or feathering effect between coarser andsmoother portions of an aluminum housing. In one embodiment, therotational speed and the translational speed along the continuous pathof the lapping tool can be fixed. In some embodiments, one or moreproperties of the lapping tool can be selected (fixed or variable alongthe cutting path) from the following: the properties can include but notlimited to (1) feed rate (translational speed in one or more of thex-axis, or y-axis directions), (2) spindle speed (rotational speed), (3)lapping tool shape and size, e.g. diameter, and (4) lapping tool cuttingmaterial. The properties of the lapping tool can be chosen to affect thepolishing time and resulting properties of the cut surface of aluminumhousing 100. The rotational and translational speeds can be selected tominimize polishing time while ensuring a quality of surface cut by thepolishing tool that can result in a preferred surface finish.

FIG. 7 illustrates a flow chart detailing a representative lappingprocess 700 in accordance with the described embodiments. Process 700can begin at 702 by pre-measuring selected surface characteristics suchas surface roughness. The measuring can be carried out by performing a3D scan, for example, and taking various contour measurements. At 704,the surface area to be lapped is processed by a lapping tool. During thet lapping process, slurry can be transported through the lapping tooland selectively delivered to a portion of the spot lapping region duringthe spot lapping process. In one embodiment, the lapping tool caninclude force sensors used to monitor in real time a force applied bythe lapping tool on the surface. In one embodiment, the lapping tool canhave a lapping pad coupled to a lapping plate having a rigid centralportion and a more flexible peripheral portion. A force applied by thelapping pad corresponding to the rigid central portion can be a maximumand the force can then be reduced at lapping pad portions correspondingto the more flexible peripheral portion. In one embodiment, the lappingtool can be translated along a lapping path with respect to the housing.A lapping path can include orbital motions and star shaped motions thatcan be used in conjunction with rotation of the housing to facilitate asmooth transition region between the spot lapping region and a remainderof the surface of the housing. At 706, surface characteristics aremeasured and if at 708 are determined to be acceptable then process 700ends otherwise control is passed back to 704.

The various aspects, embodiments, implementations or features of thedescribed embodiments can be used separately or in any combination.Various aspects of the described embodiments can be implemented bysoftware, hardware or a combination of hardware and software. Thedescribed embodiments can also be embodied as computer readable code ona computer readable medium for controlling manufacturing operations oras computer readable code on a computer readable medium for controllinga manufacturing line used to fabricate thermoplastic molded parts. Thecomputer readable medium is any data storage device that can store datawhich can thereafter be read by a computer system. Examples of thecomputer readable medium include read-only memory, random-access memory,CD-ROMs, DVDs, magnetic tape, optical data storage devices, and carrierwaves. The computer readable medium can also be distributed overnetwork-coupled computer systems so that the computer readable code isstored and executed in a distributed fashion.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the invention.However, it will be apparent to one skilled in the art that the specificdetails are not required in order to practice the invention. Thus, theforegoing descriptions of specific embodiments of the present inventionare presented for purposes of illustration and description. They are notintended to be exhaustive or to limit the invention to the precise formsdisclosed. It will be apparent to one of ordinary skill in the art thatmany modifications and variations are possible in view of the aboveteachings.

The embodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, to therebyenable others skilled in the art to best utilize the invention andvarious embodiments with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

What is claimed is:
 1. An apparatus for creating a gradual transitionregion between an accessory region and a surrounding exterior surfaceregion of a housing, the apparatus comprising: a lapping tool, thelapping tool comprising: a lapping pad, comprising: a centerpointsurrounded by a central portion, and a peripheral portion, whereinduring a lapping operation the centerpoint of the lapping pad iscompelled to follow a lapping path, the lapping path comprising aplurality of lapping segments, each lapping segment substantiallycrossing the accessory region at an angle different than a precedinglapping segment and each lapping segment putting the peripheral portionof the lapping pad in tangential contact with a central area of theaccessory region, thereby creating the gradual transition region.
 2. Theapparatus as recited in claim 1, wherein the created gradual transitionregion provides a gradual transition between a fine finish associatedwith the accessory region and a coarser finish associated with thesurrounding exterior surface region.
 3. The apparatus as recited inclaim 2, wherein a geometric configuration of the polishing path causesthe peripheral portion of the lapping pad to come in more frequentcontact with the central area of the finished accessory region than withany other portion of the surrounding exterior surface region.
 4. Theapparatus as recited in claim 3, wherein the lapping tool furthercomprises a lapping plate mechanically coupled to the lapping pad, thelapping plate comprising: a rigid central portion; and a flexibleperipheral portion mechanically coupled to the rigid central portion,wherein the flexible peripheral portion allows a greater force to beapplied across the central portion of the lapping pad and smaller forcetowards the peripheral portion of the lapping pad during a lappingoperation.
 5. The apparatus as recited in claim 3, wherein the lappingtool further comprises a lapping plate mechanically coupled to thelapping pad, the lapping plate comprising: a composite plate having arigid central portion and a more flexible periphery, the change inrigidity occurring gradually between the rigid central portion and theperiphery.
 6. The apparatus as recited in claim 3, wherein the housingis mechanically coupled to a stage having at least four degrees offreedom, the stage configured to maneuver the housing substantiallyparallel with respect to the lapping pad, the maneuvering of the stagecompelling the lapping pad to follow the lapping path with respect tothe housing.
 7. The apparatus as recited in claim 6, wherein the stageis configured to rotate around a first axis offset from a second axis ofrotation associated with the lapping plate as it continues to compel thelapping tool to follow the lapping path by translation in X and Y axes,wherein the offset between the first and second axes randomizes thelapping path.
 8. The apparatus as recited in claim 7, wherein thelapping path has a star shaped geometry.
 9. The apparatus as recited inclaim 7, wherein the housing includes a plurality of accessory regionsand the polishing path causes the lapping pad to create a gradualtransition region covering the plurality of accessory regions.
 10. Themanufacturing method as recited in claim 6, wherein a diameter dimensionof the lapping pad is between about 35 and 45 mm.
 11. A manufacturingmethod, comprising: mounting a housing to a stage, the housingcomprising: a first region, a second region surrounded and defined bythe first region, and a transition region disposed between the firstregion and the second region; positioning a lapping tool in physicalcontact with a portion of the second region during a lapping operation,the lapping tool comprising a lapping pad having a central portion and aperipheral portion; and finishing the transition region by causing thelapping pad to follow a lapping path, the lapping path comprising aplurality of lapping segments, each lapping segment substantiallycrossing the second region at an angle different than a precedinglapping segment and each lapping segment putting a peripheral portion ofthe lapping pad in tangential contact with a central area of the secondregion.
 12. The manufacturing method as recited in claim 11, wherein thefinished transition region provides a gradual surface texture transitionbetween the second region and the first region.
 13. The manufacturingmethod as recited in claim 12, further comprising: performing a threedimensional scan of the housing prior to beginning a lapping operation,wherein the lapping path can be adjusted to target the transitionregion.
 14. The manufacturing method as recited in claim 12, whereinafter a lapping operation a subsequent lapping operation is performed ifthe transition region is not completely finished.
 15. The manufacturingmethod as recited in claim 12, wherein the finishing the transitionregion comprises rotating the housing in an axis of rotation offset fromthe lapping tool axis of rotation while the lapping path is beingfollowed.
 16. A lapping assembly, comprising: a lapping tool comprisinga rotating lapping plate coupled to a lapping pad; a force sensorcoupled to the lapping tool for regulating pressure exerted by thelapping tool; and a stage configured to maneuver a housing in a planesubstantially parallel with the lapping pad during a lapping operation,the housing having an exterior surface with an accessory region and asurrounding surface region, wherein during a lapping operation thelapping pad is compelled to follow a lapping path, the lapping pathcomprising a plurality of lapping segments, each lapping segmentsubstantially crossing the accessory region at an angle different than apreceding lapping segment and each lapping segment putting a peripheralportion of the lapping pad in tangential contact with a central area ofthe accessory region, thereby creating a gradual transition regionbetween the accessory region and the surrounding surface region.
 17. Thelapping assembly as recited in claim 16, wherein the stage has at least6 degrees of freedom, and wherein the degrees of freedom of the stageallow the lapping tool to establish the gradual transition region acrossa three dimensional curved surface portion of the housing.
 18. Thelapping assembly as recited in claim 16, wherein the lapping tool has achamfered edge portion configured to prevent scratching of the metalhousing when a misalignment between the lapping tool and the metalhousing takes place.
 19. The lapping assembly as recited in claim 16,wherein the lapping tool further comprises a slurry delivery conduithaving a plurality of slurry delivery branches configured within thelapping plate, wherein the rotational motion of the lapping tool drawsslurry down through the slurry conduit as a result of a geometricalconfiguration of the plurality of slurry delivery branches.
 20. The spotlapping assembly as recited in claim 16, wherein the housing is analuminum housing and the accessory region has a mirror finish prior tothe lapping operation.